Manganese(II) hydroxide

Manganese(II) hydroxide
Names
Other names
Manganese dihydroxide, manganese hydroxide, Manganous hydroxide, Pyrochroite
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.126.826 Edit this at Wikidata
EC Number
  • 606-171-3
  • InChI=1S/Mn.2H2O/h;2*1H2/q+2;;/p-2
    Key: IPJKJLXEVHOKSE-UHFFFAOYSA-L
  • [OH-].[OH-].[Mn+2]
Properties
H2MnO2
Molar mass 88.952 g·mol−1
Appearance white to pink solid
Density 3.258 g/cm3
Melting point 140 °C (284 °F; 413 K) decomposes
0.00034 g/100 mL at 18 °C.[1]
Solubility soluble in acid
1.68
Structure
hexagonal
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Manganese(II) hydroxide is the inorganic compound with the formula Mn(OH)2. It is a white solid although samples darken quickly upon exposure to air owing to oxidation. It is poorly soluble in water.

Structure, preparation, and reactions

Mn(OH)2 adopts the brucite structure, i.e. the arrangement of the atoms in the crystal are the same as the arrangement of the atoms in Mg(OH)2. The Mn(II) centers are bonded to six hydroxide ligands. Each hydroxide ligand bridges to three Mn(II) sites. The O-H bonds are perpendicular to the planes defined by the oxygen atoms, projecting above and below these layers.[2]

Manganese(II) hydroxide precipitates as a solid when an alkali metal hydroxide is added to an aqueous solution of Mn2+ salt:[3]

Mn2+ + 2 NaOH → Mn(OH)2 + 2 Na+

Manganese(II) hydroxide oxidises readily in air, as indicated by darkening of samples.

The compound adopts the brucite structure, as do several other metal dihydroxides.

References

  1. ^ Lide, David R., ed. (2006). CRC Handbook of Chemistry and Physics (87th ed.). Boca Raton, FL: CRC Press. ISBN 0-8493-0487-3.
  2. ^ Lutz, H.D.; Möller, H.; Schmidt, M. (1994). "Lattice vibration spectra. Part LXXXII. Brucite-type hydroxides M(OH)2 (M = Ca, Mn, Co, Fe, Cd) — IR and Raman spectra, neutron diffraction of Fe(OH)2". Journal of Molecular Structure. 328: 121–132. doi:10.1016/0022-2860(94)08355-x.
  3. ^ H. Lux "Manganese(IV) Hydroxide" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1456.